I don’t have experience with those units, but by all accounts they are all very nice. BUT you’ll want to be very careful in matching phono stage to your cartridge -- while ALSO considering future cartridge upgrades; again, your Prime deserves it!
You’re currently using a 5mV MM cart, and that ARC’s gain of 57.5 dB is gonna be WAY too hot for that. That’s far from optimal, for both the phono stage and the downstream preamp (no overload headroom). However, that ARC would be perfect for MC cartridges with outputs from roughly 0.45 mV to 1.0 mV, for which I believe there are many fine choices e.g. Clearaudio, Ortofon Cadenza, Lyra, Benz "medium" output models, etc.
The 834p will do fine in MM mode with MM carts. For MC carts, this unit is said to be improved by bypassing its internal SUT with a higher quality outboard one. But besides that, its MC gain of 70dB might be just a bit too hot for the medium output MC carts that would’ve paired well with the ARC -- here you’d really want 0.2-0.4 mV carts, which is the territory of Koetsu Platinums, Ortofon Windfeld/A95/Anna, Benz "low" outputs, etc.
The Liberty unit is endlessly shilled by its maker here, but honestly it looks really darn versatile. If I had to guess from its specs, it will pair well with a wider range of cartridges than the other 2 stages. Though I love a good tube stage (I run a Rogue Ares Magnum, which I think is fabulous), I’d be tempted by this one in your shoes, given these 3 options. But also, maybe look at the Rogue Triton and Ares.
My Ares has a similar gain structure to that EAR unit (72 dB in MC mode), and it pairs brilliantly with a 0.3mV Koetsu. With a 0.45 mV Ortofon Cadenza it's still good, but slightly suboptimal; that same Cadenza shines on a 60 dB Sonic Frontiers Phono 1. But of course, the Koetsu lacks dynamics and sounds rather lifeless on that Sonic Frontiers!
